The Missing Key

The case file

A glass paperweight vanished from the evidence locker. Four people with access were questioned, and each made exactly one statement. Who took the glass paperweight?

The rule: Exactly 1 of the four statements is true. The other 3 are false.

The clues

1. Tom Beck said, "I took it."
2. Grace Ivers said, "I took it."
3. Alba Finch said, "Grace Ivers took it."
4. Lena Brooks said, "I didn't take it."

Who did it?

1. Lena Brooks
2. Grace Ivers
3. Alba Finch
4. Tom Beck

The verdict

Alba Finch

Only Alba Finch fits -- then exactly 1 of the four statements are true (Lena Brooks's statement). Not Lena Brooks: if Lena Brooks had taken the glass paperweight, 0 of the four statements would be true -- but exactly 1 are. Not Grace Ivers: if Grace Ivers had taken the glass paperweight, 3 of the four statements would be true -- but exactly 1 are. Not Tom Beck: if Tom Beck had taken the glass paperweight, 2 of the four statements would be true -- but exactly 1 are.